Liquid crystal compounds and materials and devices containing them

Abstract

A novel liquid crystal compound has the molecular structure: ##STR1## where R is an alkyl group, which may contain up to 18 carbon atoms and which may be normal or branched and may contain a chiral center, ##STR2## is a bicyclo (2.2.2) octane ring, --X-- is and Y is a cyano group CN or R 1 or OR 1 where R 1 has the same definition as R. The compound may be used in mixtures with other liquid crystal compounds in the same or other families and the compound or mixtures may be used in known liquid crystal devices, eg the twisted nematic and cholesteric-to-nematic phase change devices, depending on its properties.

We claim: 
     
       1. A liquid crystal compound having a molecular structure where R is an alkyl group; ##STR25## is a bicyclo-[2.2.2]-octane ring; X is a 1,4 phenylene group ##STR26## a 4,4' biphenylyl group ##STR27## or a 2,6 naphthyl group ##STR28## Y is a cyano group, an alkyl group or an alkoxy group; and n is 0, 1 or 2.   
     
     
       2. A liquid crystal compound as claimed in claim 1 and wherein n is 0, Y is CN and R is an n-alkyl group having from one to ten carbon atoms. 
     
     
       3. A liquid crystal compound as claimed in claim 1 and wherein n is 0, Y is CN and R is an alkyl group having from three to ten carbon atoms and containing a chiral centre. 
     
     
       4. A liquid crystal compound as claimed in claim 1 and wherein n is 1, Y is CN and R is an n-alkyl group having from one to ten carbon atoms. 
     
     
       5. A liquid crystal compound as claimed in claim 1 and wherein n is 1, Y is CN and R is an alkyl group having from three to ten carbon atoms and containing a chiral centre. 
     
     
       6. A liquid crystal compound as claimed in claim 1 and wherein n is 2, Y is CN and R is an n-alkyl group having from one to ten carbon atoms. 
     
     
       7. A liquid crystal compound as claimed in claim 1 and wherein n is 2, Y is CN and R is an alkyl group having from three to ten carbon atoms and containing a chiral centre. 
     
     
       8. A liquid crystal compound as claimed in claim 1 and wherein the compound is ##STR29## 
     
     
       9. A liquid crystal compound as claimed in claim 1 and wherein the compound is ##STR30## 
     
     
       10. A liquid crystal compound as claimed in claim 1 and wherein the compound is ##STR31## 
     
     
       11. A liquid crystal compound as claimed in claim 1 and wherein the compound is ##STR32## 
     
     
       12. A liquid crystal compound as claimed in claim 1 and wherein the compound is ##STR33## 
     
     
       13. A liquid crystal compound as claimed in claim 1 and wherein the compound is ##STR34## 
     
     
       14. A liquid crystal compound as claimed in claim 1 and wherein the compound is ##STR35## 
     
     
       15. A liquid crystal compound as claimed in claim 1 and wherein the compound is ##STR36## 
     
     
       16. A liquid crystal compound as claimed in claim 1 and wherein the compound is ##STR37## 
     
     
       17. A liquid crystal compound as claimed in claim 1 and wherein the compound is ##STR38## 
     
     
       18. A liquid crystal compound as claimed in claim 1 and wherein the compound is ##STR39## 
     
     
       19. A liquid crystal compound as claimed in claim 1 and wherein the compound is ##STR40## 
     
     
       20. A liquid crystal compound as claimed in claim 1 and wherein the compound is ##STR41## 
     
     
       21. A liquid crystal compound as claimed in claim 1 and wherein the compound is ##STR42## 
     
     
       22. A liquid crystal compound as claimed in claim 1 and wherein the compound is ##STR43## 
     
     
       23. A liquid crystal compound as claimed in claim 1 and wherein the compound is ##STR44## 
     
     
       24. A liquid crystal compound as claimed in claim 1 and wherein the compound is ##STR45## 
     
     
       25. A liquid crystal compound as claimed in claim 1 and wherein the compound is ##STR46## 
     
     
       26. A liquid crystal compound as claimed in claim 1 and wherein the compound is ##STR47## 
     
     
       27. A liquid crystal compound as claimed in claim 1 and wherein the compound is ##STR48## 
     
     
       28. A liquid crystal compound as claimed in claim 1 and wherein the compound is ##STR49## 
     
     
       29. A liquid crystal compound as claimed in claim 1 and wherein the compound is ##STR50## 
     
     
       30. A liquid crystal material comprising a mixture of compounds at least one of which is a compound as claimed in claim 1. 
     
     
       31. A liquid crystal material comprising a mixture of compounds wherein the mixture includes at least two compounds as claimed in claim 1. 
     
     
       32. A liquid crystal material as claimed in claim 30 and wherein the mixture includes also at least one compound of the form ##STR51## where R' 1  is an alkyl or alkoxy group, n'=0 or 1. 
     
     
       33. A liquid crystal electro-optic device comprising two adjacent dielectric substrates at least one of which is optically transparent, a layer of liquid crystal material between the substrates and electrodes on the inner surfaces of the substrates to allow an electric field to be applied across the material, characterised in that the liquid crystal material comprises at least one compound as claimed in claim 1. 
     
     
       34. A device as claimed in claim 33 and wherein the device is a twisted nematic effect device. 
     
     
       35. A device as claimed in claim 33 and wherein the device is a cholesteric-to-nematic phase change effect device.